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Talk:Epstein Drive/@comment-178.41.242.162-20180114145735
To those who say how the Epstein drive is impossible because you need to couple the high specific impulse of ion drives with high thrust of atomic rockets, do you realize that even the most conservative realistic fusion drive designs have specific impulse far higher than any ion drive? High thrust, low Isp? That's a chemical rocket! Here is an engine list, http://www.projectrho.com/public_html/rocket/enginelist.php . The fusion drive designs presented there have a specific impulse of 5140 s. up to 1313 970 s.. To compare, ion drives have an Isp of 8000 s. It is completely wrong to claim that a high thrust, high Isp drive is impossible, we just don't have the technology to make one yet. The jet does not even have to be dense - fusion plasma is thin, but VERY hot, thus it has an extreme exhaust velocity. There ARE some unrealistic traits that the Epstein drive has as presented by the show, but in itself, it is fairly plausible: 1. Magnetic tokamak style fusion is likely insufficient for a torchship (high G + high Isp, there are many non torchship fusion designs) as explained here http://www.projectrho.com/public_html/rocket/enginelist.php#fusiondrive under "Torchship fusion". Inertial confinement fusion (basically using laser/ion beams to heat up and compress small pellets of fusion fuel that explode in rapid succesion behind the ship) seems to be the best way to achieve that, as it solves the "Scott Manley said the ship will vaporize" problem (because the vaporization will only occur if you try to contain the reaction inside the ship). The calculated distance to keep a ship safe for a 1 G burn is 66 meters, 22-30 meters with heat radiators. The high G burns are the unrealistic part, but constant 0.3 G or 1 G thrust seems a lot more likely. The De-He3 design mentioned in my link is not capable of a constant 1 G burn for more than 2 days, but could presumably do a 0.3 G burn for far longer, enough to do constant thrust trajectories. It doesn't mean the "magnetic bottle" comment is false through, a magnetic field would certainly help to direct the products of inertial fusion for better efficiency. Alternatively, it could be a P-Jet magneto-inertial fusion system, which is a real theoretical fusion system most suspiciously similiar in performance to Epstein drive http://www.projectrho.com/public_html/rocket/enginelist.php#pjmif . 2. I think real ships with drives that powerful would have at least a few heat radiators. A 1 G fusion torchship would need to detonate the fusion pellets or plasma blobs 60 meters from the ship, using the best fusion option, De-He3. Radiators could reduce that distance to 22-30 meters, which would ease fuel compression and heating, as it is always easier to focus the beams properly when it's closer rather than faster. 3. Responding to this "Also an FYI: the more efficient the rocket engine, the less visible the drive plume. During Space Shuttle launches, the SRBs generate bright & huge plumes while the engines on the Shuttle itself were nearly invisible. The Shuttle's engines possess a much higher drive efficiency than the engines on the SRBs." - this is completely wrong. A drive with Epstein's power output would be visible from Earth with naked eyes even if it was on Pluto. The visibility of Space Shuttle's plume has nothing to do with efficiency, it is so faint because it contains no incandescent soot that is present in kerosene and solid rockets. A fusion drive is preferably very focused, but an IC fusion drive is still pretty much making a stream of mini nuclear explosions, it is not a laser beam. Too many people here assume things based on chemical rockets. Those are crap compared to well... everything. Even 1960s nuclear rockets had 2.5x the specific impulse but were never used because the public went chickenshit on anything nuclear. They look like this https://www.youtube.com/watch?v=GmxPRCyR-Co . Not bright, they were relatively low thrust, but hardly invisible. Scott Manley never said that the heat would vapourize every ship ever. A ship as small as Epstein's yacht, with no radiators, using a purely magnetic confinement system that keeps the reaction in the drive nozzle? Yeah, it would go poof. What I find most unreleastic about the Expense show (as opposed to the books where they're explicitly stated to have colossal blinding jets of gas) is how the plumes are depicted as big natural gas flames from a stove. In reality, Epstein's yacht would have huge radiator panels on each side, use a magnetoinertial fusion system and the jet of flame would be pulsating 30 meters behind the ship. The way to make torchships is to contain the reaction outside the ship. As for propellant, the nozzle made of ablative IS the propellant, as it evaporates when hit by the energy from the fusion pellets exploding behind the ship! Yes, the most likely torchship design is a solid propellant fusion rocket! Basically, miniaturized, far higher tech Project Orion. Fusion technology enables the use of far smaller pellets instead of bombs and an ablative nozzle enables far better efficiency than a shock absorbing pusher plate.